Microbiologists Hold the Secrets to Making Perfect Cheese

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Microbiologists Hold the Secrets to Making Perfect Cheese

Wheel of Brie Cheese on White

Brian Leatart/Getty Images

Cheese has so many tasty personalities. Ricotta quietly complements lasagna with creamy mildness, while the zing of a five-year-old cheddar dominates any carb you pair with it. Brie is cooperative, letting you spread it over a cracker, while blue cheese just falls apart whenever you bring a knife to it.

These cheeses—despite their different characters—have one thing in common: They’re ridiculously delicious. But what exactly makes them that way? What kind of magic turns milk into the rich, tangy, nutty, fruity, stinky wonder that is cheese—and how do cheesemakers make sure they end up with exactly the variety they’re looking for? It’s not magic: It’s microbiology. And it take a special kind of scientist to wield its ancient power.

All of these different kinds of cheese have the same humble beginnings. The process starts with curdling milk—converting it from liquid to solid. This usually consists of two steps. First, cheesemakers add lactic acid bacteria, which converts lactose, the sugar in milk, into lactic acid. Then they add rennet, which breaks down milk proteins and makes the molecules collapse into each other, turning milk into white curds. At this point, you’ve essentially got ricotta—fresh, creamy, and a little boring.

Here’s where things get interesting: To get the cheese that they want, cheesemakers will add different combinations of digestion-friendly microbes such as yeast, mold, and bacteria along with the lactic acid bacteria and the rennet. And to ensure they end up with the right combination, they turn to science.

Ben Wolfe, a microbiologist at Tufts University, is a cheese scientist: He works with cheesemakers to analyze their product’s microbes and achieve maximum tastiness. Many cheese companies even have in-house microbiologists to analyze these microbiomes—sometimes even using DNA sequencing—to help them control the flavor.

How do microbes create complex flavors? First, they break down the proteins and fats in milk—creating different-tasting cheese depending on the microbes present. For example, some yeasts produce compounds called esters that can lend a fruity flavor to the cheese, and the telltale stench of limburger comes from mold breaking down the protein in milk into sulfur compounds, small enough to become airborne.

Cheesemakers use microbial variety to control how cheese tastes. Take camembert, for example, which resembles brie originating from France. To make the white, skin-like rind, cheesemakers actually spray mold on the curds, which breaks down the cheese from the outside. They can even cater the microbial variety to their customers’ tastes. “Camembert made by American cheese producers are buttery and mushroomy," says Wolfe. "Traditional camembert is a stinky beast.”

Jasper Hill Farm, one of the cheesemaking companies Wolfe has worked with, has over 190 different microbes in their milk prior to pasteurization. “For some cheeses, you can have a whole bouquet of flavors from over a hundred different compounds,” says Wolfe. “All the chemical components in the milk are essentially being restructured and reorganized in different formations that look, taste, and smell different.”

The more control you have over the microbes, the more consistent your cheese will taste. Cheesemakers can use pasteurization to control the flavor of the cheese: Pasteurization kills off all microbes, which essentially provides cheesemakers with a blank canvas to paint the flavor profile of their cheese.

But not all cheesemakers care for consistency. For industrial-scale cheesemaking companies like Kraft, consistent flavor is important, so they always pasteurize their cheese, and don’t use too many microbial strains. For smaller, so-called artisanal cheesemakers, variation and complexity is more important than consistency, so they will use lots of different types of microbes, sometimes even using unpasteurized milk, which is less predictable and allows for more cheesemaking creativity. (But take note: Unpasteurized milk—or raw milk—is a polarizing topic. It's got different FDA regulations because it's more likely to contain disease-causing pathogens, but hardcore cheese enthusiasts get riled up even at the hint of new restrictions.)

Microbe strains—despite the panoply of flavors—don’t necessarily have much genetic variation. “Among different yeast strains, it’s like the difference between me and my sister,” says Sayer Dion, the in-house microbiologist for Jasper Hill Farm. “We are of the same genus and the same species. However, our slight differences in DNA are why our hair color is different.” These subtle differences in DNA can result from environment—for example, constantly taking yeast in and out of a freezer will stress the cells out and cause mutations that change the microbes’ fermentation process.

All this, of course, is a very fancy way of talking about a process that has been carefully cultivated over centuries without the input of microbiologists. “Cheese is intentional delicious rot that a cheesemaker controls through the whole process of aging,” says Wolfe. So there you go. The varieties of cheese are just all the ways that milk can rot.